Current standards and Threshold Limit Values for exposures to silica dust are based to a large extent on studies in the Vermont granite industry. Since 1935 the North Carolina Industrial Commission, has collected environmental data to describe dust exposures in the States' dusty trades, and has maintained work histories and obtained annual chest X-rays for detection of silicosis among workers employed in these trades. Approximately 4,500 environmental samples have been taken to describe dust exposures in some 200 mines and minerals industry plants. More than 200,000 chest X-rays have been taken, and 759 workers have had diagnoses of silicosis; of these some 490 were first diagnosed in the period 1950 through 1979. The great amount of data which have been accumulated in this mines and minerals industry surveillance program have not been systematically analyzed. The State Board of Health and the Industrial Commission have agreed to cooperate with the School of Public Health, University of North Carolina, in a research project for such analysis. It is proposed to use the environmental and work history data to develop quantitative dust exposure histories for silicosis cases and for matched non-silicotic controls. Analyses to detect and describe associations between exposures to dust and occurrence of silicosis for the various mining and minerals industries and worker populations in the North Carolina program will be done. The results of this study will supplement information currently available, and upon which current standards are based.